Near maximum likelihood demodulation for M-ary orthogonal signalling

A new coherent demodulation method for M-ary orthogonal signals is presented. The technique is well suited to channels exhibiting coherence over a group of symbols such as burst and slow frequency hopping channels. The method achieves performance close to that of coherent demodulation with perfect channel estimates. In code division multiple access (CDMA) systems, performance gains afforded by this demodulation scheme translate directly into an increase in capacity. Simulation results are presented for the reverse link of the Qualcomm CDMA system. The results show that the system operating point can be reduced by as much as 1.25 dB